1. Field of the Invention
This invention relates to a scleral plug for occluding a hole in the eye and for controlled irrigation during vitreo-retinal surgery in order to maintain a closed system during the procedure, and angled forceps for handling the plugs.
2. Description of Related Art
Modern vitreo-retinal surgery allows ophthalmologists to diagnose and treat diseases of and injuries to the posterior segment of the eye. Vitreo-retinal surgery involves the use of small needle instruments to remove, for example, the vitreous humor, hemorrhage, scar tissue, infection or foreign bodies.
A typical three port vitrectomy utilizes an infusion cannula, which maintains a preset tension in the eye, and multiple hand-held instruments for illumination, cutting, grasping, and suction. A carefully constructed environment must be maintained within the eye at all times for these procedures to be successful. The surgeon uses microsurgical techniques to manipulate the delicate tissue within the eye. The instruments are introduced into the vitreous cavity through sclerotomies, or small holes, in the area of the pars plana ciliaris.
Small steel plugs are utilized during vitreo-retinal surgery to occlude the sclerotomy sites when instruments are not inserted through these access holes in the sclera. The plugs of the prior art have a straight shaft and a cap on one end. Inserting these plugs into the access holes allows the surgeon to maintain a closed system, which is important for the prevention of pressure loss, egress of fluid or globe contents, and entrance of bacteria or debris. These access holes, or sclerotomies, are manipulated by repeated passing of instruments and will tend to stretch and enlarge, allowing the plugs to slip out. There is a need for a scleral plug that will remain in place during vitreo-retinal surgery, allowing a surgeon to maintain a closed system.
Proliferative vitreoretinopathy (PVR) is the leading cause of failure of retinal detachment repair. Although the etiology is somewhat controversial, one theory implicates the retinal pigment epithelial (RPE) cells. RPE cells are xe2x80x9cworkhorsexe2x80x9d type cells with fibroblastic, or scar forming, potential. During formation of retinal tears or treatment with cryotherapy, these RPE cells may be released into the vitreous cavity, increasing the chances of PVR. Currently, during a vitrectomy, the surgeon can irrigate these cells from the eye using a flute needle, called a Charles Needle. This type of irrigation requires the surgeon to manually hold instruments in the eye for 30-60 seconds or more. Thus, there is a need for a plug that would allow controlled egress of fluid without requiring the surgeon""s strict attention and active manipulation.
Forceps used in the art to manipulate scleral plugs are currently reverse actingxe2x80x94they grip until you squeeze to release. Thus, the instrument will hold a plug until placed and released by the surgeon. Current forceps have a long, angled tip. The length of the tip, combined with the size of the tiny plug, makes it difficult to place a plug in a sclerotomy. Thus, there is a need for forceps that allow easier placement and more exacting control over placement of plugs.
One embodiment of this invention is a scleral plug with a bulbous, rather than straight, shaft. This plug remains firmly in position during vitreo-retinal surgery and minimizes the likelihood that the plug will slip out of position. In order to maintain a watertight fit while taking care not to stretch the sclerotomy, the proximal end of the shaft has a smaller diameter than the distal bulbous tip. The portion of the shaft having a smaller diameter is of a length to accommodate the thickness of the sclera.
A further embodiment,of this invention relates to a plug that functions as a small bore cannula. This plug has a shaft lengthened to about 6 mm and a lumen with an opening through the cap of the plug. Fluid flows into the eye through the infusion cannula until the eye reaches a predetermined pressure. When using the plugs of the prior art, any breach in the system allows fluid to escape uncontrolled, e.g. a leak or an unplugged sclerotomy. A plug with a lumen according to this embodiment allows the surgeon to control the breach in the system. In particular, the surgeon may irrigate the intraocular cavity to remove RPE cells while still maintaining a controlled environment. These RPE cells initially may be released from their sub-retinal location as a result of trauma or retinal breaks. The release of RPE cells are believed to cause PVR, which results in loss of vision. It is important to irrigate the eye so that the RPE cells are expelled from the vitreous cavity. Replacing a standard plug with this cannulated plug, or adding a lumen to the bulbous plug of this invention, allows controlled irrigation of fluid from the eye. If immediate cessation of the irrigation is needed, it can be accomplished simply by placing a finger over the external opening of the lumen.
Fluid turbulence may cause even healthy retina to be drawn toward a sclerotomy and damaged. It is important that retina is not expelled from the intraocular cavity through the sclerotomy site. The cannulated plug of this invention avoids expulsion of the retina. The length of the shaft of this cannulated plug locates the opening of the lumen more centrally within the vitreous cavity and far enough to avoid disturbing the retina.
The forceps of this invention have a shortened tip for ease in handling the minute plugs utilized in vitreo-retinal surgery, while maintaining the overall length of the handles and their reverse-action grip.
Accordingly, it is an object of this invention to provide a scleral plug with a bulbous tip so that the plug remains in position during vitreo-retinal surgery.
It is a further object of this invention to provide a cannulated plug for controlled irrigation during vitreo-retinal surgery.
It is a further object of this invention to provide a cannulated plug that avoids expulsion of the retina.
It is another object of this invention to provide forceps with shortened tips for ease in handling scleral plugs.